Induced Polarization Imaging and Other Topics Associated with the Solid Immersion Lens

Abstract

An induced evanescent polarization imaging system and associated topics using a solid immersion lens (SIL) are demonstrated in this dissertation. The physics and properties of induced polarization signal of the SIL are studied by both simulations and experiments. In the SIL optical system, with a linearly-polarized incident illumination light at the entrance pupil, an orthogonal component of polarization is induced upon reflection from the SIL. This orthogonal polarization signal contains information of both air gap height h between the bottom of the SIL and the top surface of the sample. It is used as the air gap control signal in the SIL system. An experimental SIL near-field microscope setup is developed and demonstrated. A compact mechanical package is developed for a standard microscope that implements a SIL on a retractable bimorph swing arm. With the compact package mounted on an inverted microscope, far-field and near-field images are obtained at the same location by moving the SIL with the swing arm. A 25 μm diameter and 0.8 μm high circular pedestal in the center of the flat portion of the SIL is fabricated, along with a conically shaped surrounding region. The image contrast enhancement, high lateral resolution and height information are obtained with induced polarization evanescent imaging using SIL. Experiments are conducted by imaging features on a patterned Si substrate. Imaging theory is used to predict optimum orientation of high-spatial-frequency samples, and a topographical image is derived from the induced polarization image through a calibration procedure. A numerical aperture of NA=1.5 is used in the experiment. Height accuracy of ± 2nm is demonstrated with a known sample. A new lithography system employing a solid immersion lens (SIL) is proposed and primitive experiment results are presented. SIL technology is a direct-writing technique, where high resolution is easily achieved without a mask.